Numerical and Experimental Studies of The Flow Through Narrow GAP

The flow in channels with characteristic dimension of the order of millimetres is of high importance for determination of losses of the devices such as small turbines, screw-type compressors and for investigation of the tip leakage flow. Since most of the contemporary studies deal with the micro or nano flows, the purpose of this work is to provide a reliable experimental data and to explore the possibilities of the numerical simulations of the present flo

Solution of the Compressible Viscous Fluid Flow past Minichannels

This paper deals with compressible viscous fluid flow past minichannels of the rectangular cross-section. The numerical solution was formulated and the results of the numerical solution were analysed including the comparsion with the experimental results which were carried out in the aerodynamics laboratory of the IT AS CR, v.v.i

Solution of parameters of compressible viscous fluid flow through a minichannel

In this paper the results of the experiment of the choked air flow through channel with characteristic dimensions: height 2mm, width 100mm, length 100mm will be presented. On the bases of the both pneumatic and optical measurements the development of the flow properties along the channel and the influence of the dissipative processes will be described. The results of the experiment will be compared to the theoretical results and to the results of the numerical simulation. At the end the comparison will be thoroughly discussed

Effects and development of the near-wall flow in the hub section of the last stage steam turbine blade

This paper deals with the investigation of three-dimensional vortex structures in the near-wall region of the blade cascade which represents the model of the hub section blading of last stage blades of a steam turbine. The investigation aims to describe the development and mutual interaction of the vortex structures and its influence on the kinetic energy losses. The analyses are based on the RANS numerical simulations and experiments conducted in the high-speed wind tunnel.\n\

Measurement on Valve III

This research report deals with the results and analysis of the pneumatic measurements of flow in the model of the high pressure steam valve system (VT1000MW)

CFD Investigation of the test facility for forced blade flutter research

With the increasing share of renewable power resources turbomachines need to be operated under a wider range of operating conditions including highly off-design regimes. Under such regimes an undesirable phenomenon of blade flutter might occur and possibly destroy the machine. To prevent this, intensive research is conducted by research teams worldwide. Blade flutter research program at the Institute of Thermomechanics of the Czech academy of sciences (IT CAS) mainly aims to advance experimental techniques for investigation of sonic and transonic blade flutter. For this purpose, the new sophisticated test facility was designed and manufactured. As part of the design process, the CFD computations were conducted in order to investigate the flow field in the test facility. This paper presents results of these computations with detailed analysis of flow structures occurring during the air flow through the stationary blade cascade

CFD Simulation of Transonic Flow Through the Tip-Section Turbine Blade Cascade Intended for the Long Turbine Blade

The paper deals with numerical simulations of transonic flow through the turbine blade cascade consisting of flat profiles. The cascade is one of variants of the tip section of ultra-long blades, which were designed for the last stage of the steam turbine. CFD simulations were realized by means of the ANSYS CFX commercial software using the γ-Reθ bypass transition model completed by the two-equation SST turbulence model. Some simulations were made only by the SST turbulence model for comparison. Numerical results were compared with experimental data. Calculations performed for two nominal regimes and two computational domains. In addition to the standard computational domain, the calculation was performed for a domain with an extended output part for the suppression of reflected shock waves. The interaction of the inner branch of the exit shock wave with the boundary layer on the blade suction side leads in the both flow regimes to the flow separation followed by the transition to turbulence. The flow structure in the blade cascade obtained for the extended domain corresponds well to experimental results

On the possible origin of a vapour cone occurring during the transonic flight in moist air

In aerodynamics as in other sciences, there are some phenomena which are widely explained in a way that under a closer look turns out to be based on wrong assumptions and thus not very convincing. One of these is the effect referred to as vapour cone or shock collar which is the cloud of condensed water of the conical shape that forms around objects travelling at transonic speeds through the moist air. This paper aims to shed light on some basic principles that might stand behind this effect and based on the simple physical model provide possible explanation and correct some of the common misconceptions which are repeated ad nauseam not only on the internet sites of aerodynamics enthusiasts but also in some textbooks

Optical and Hot-Film Measurements of the Boundary Layer Transition on a Naca Airfoil

This study explores the possibilities of identifying position of a boundary layer transition using hot film measurements complemented by classical optical methods i.e. interferometry and schlieren method. The subject of the measurement is a NACA 0010-64 airfoil with varying leading edge surface quality corresponding to smooth surface and rough surface with Ra ~ 50 and Ra ~ 100. Measurements are performed at several subsonic regimes and a transonic regime. Despite several shortcomings of the experimental setup, the method proved to be useful in providing information on the boundary layer transition. Measurements show that in the case of smooth leading edge, the onset of the boundary layer transition shifts upstream with increasing inlet Mach number and the major portion of the boundary layer is transitional. This is in accordance with other published results on the boundary layer transition on this kind of airfoils [1]. In all cases with the rough leading edge, the complete transition takes place on the rough portion of the surface already

Clearance gap flow: extended pneumatic measurements and simulations by discontinuous Galerkin finite element method

In the present paper, new results of measurements of the compressible viscous fluid flow in narrow channels with parallel walls under the conditions of aerodynamic choking are presented. Investigation was carried out using the improved test section with enhanced capability to accurately set the parallelism of the channel walls. The measurements were performed for the channels of the dimensions: length 100 mm, width 100 mm and for various heights in the range from 0.5 mm to 4 mm. The results in the form of distribution of the static pressure along the channel axis including the detailed study of the influence of the deviation from parallelism of the channel walls are compared with previous measurements and with numerical simulations performed using an in-house code based on Favre averaged system of Navier-Stokes equations completed with turbulence model of Spalart and Allmaras and a modification of production term according to Langtry and Sjolander. The spatial discretization of the governing equations is performed using the discontinuous Galerkin finite element method which ensures high order spatial accuracy of the numerical solution